Chemical amplified resist, polymer for the chemically amplified resist, monomer for the polymer and method for transferring pattern to chemically amplified resist layer

ABSTRACT

Chemically amplified resist is produced on the basis of vinyl polymer having 3-oxo-4-oxabicyclo [3.2.1 ]octane-2-yl group expressed by general formula (1)  
                 
 
     where each of L 1 , L 2 , L 3 , L 4 , L 5  and L 6  is selected from the group consisting of hydrogen atom and alkyl groups having the carbon number from 1 to 8, and the hydrogen atom and/or the alkyl group at L 5  and L 6  are replaced with alkylene groups having the carbon number from 1 to 10 and bonded to each other for forming a ring so that the resist exhibits high transparency to light equal to or less than 220 nm wavelength, large resistance against dry etching and good adhesion to substrates.

FIELD OF THE INVENTION

[0001] This invention relates to compounds used in photoresist and, moreparticularly, to chemically amplified photoresist sensitive tofar-ultraviolet light equal in wavelength to or less than 220nanometers, polymer used for producing the chemically amplified resist,monomer for producing the polymer and a method for transferring apattern to a chemically amplified resist layer.

DESCRIPTION OF THE RELATED ART

[0002] Pattern images are sequentially transferred to semiconductorwafers in processes for fabricating semiconductor devices, and designrules have been renewed in the fabrication process. Now, semiconductordevices are designed under sub-micron rules, and requirements for thephotolithography get sever and sever.

[0003] Manufacturers require 0.13 micron patterns for 1 giga-bit DRAMs(Dynamic Random Access Memory), and research and development efforts arebeing made for the photolithography used in the ultra large scaleintegration. 193-nanometer wavelength ArF excimer laser lithography isdisclosed by Donald C. Hofer et. al. in “193 nm Photoresist R & D: TheRisk & Challenge”, Journal of Photopolymer Science and Technology, vol.9, No. 3, pages 387-397, 1996. The ArF excimer laser lithographyrequires new photo-resist. The ArF excimer laser system is expensive,and the gaseous mixture used therein is short in lifetime. In thesecircumstances, the new photoresist is expected to be highly sensitive tothe ArF excimer laser light as well as the high resolution from theviewpoint of the cost performance.

[0004] The chemically amplified photoresist is attractive. Thechemically amplified photoresist contains photo-acid generator, whichaccelerates the chemical reaction in the photoresist. A typical exampleof the chemically amplified photoresist is disclosed in Japanese PatentApplication laid-open No. 2-27660. The prior art chemically amplifiedphotoresist contains triphenylsulfonium hexafluoroarsenate and poly(p-tert-butoxycarbonyloxy-α-methyl styrene). The prior art chemicallyamplified photoresist is presently used in KrF excimer laser lithographyas taught by Hiroshi Itoh and C. Grantwillson, American Chemical SocietySymposium Series, vol. 242, pages 11-23, 1984.

[0005] When the chemically amplified photoresist is exposed to thelight, proton acid is generated from the photo-acid generator. Theproton acid reacts with the copolymer in the heat treatment after theexposure to the light. The amount of reaction per photon, i.e.,photoreaction efficiency is enhanced through the acid-catalyzedreaction. Although the photoreaction efficiency is less than 1 in theconventional photoresist, the chemically amplified photoresist achievesthe photoreaction efficiency greater than 1, and most of new products ofphotoresist presently developed are of the type chemically amplified.

[0006] The ArF excimer laser is an example of the short-wavelength bandequal to or less than 220 nanometers. The photoresist available for thephotolithography in the short-wavelength band is expected to betransparent to the exposure light and large in resistance against dryetching. The prior art products of photoresist, which are responsive tog-line with 438 nanometer wavelength, i-line with 365 nanometerwavelength or KrF excimer laser light with 248 nanometer wavelength,contain copolymer having the structural unit with the aromatic ring suchas novolak resin or poly (p-vinylphenol), and the aromatic ring makesthe copolymer resistive against the dry etching.

[0007] Although the copolymer with the aromatic ring is preferable forthe KrF excimer laser light or the long wavelength rays, the copolymerexhibits strong light absorption to the light in the short wavelengthband equal to or greater than 220 nanometer wavelength. In fact, whenthe prior art photoresist based on the copolymer is exposed to the ArFexcimer laser light, most of the ArF excimer laser light is absorbed inthe surface portion of the prior art photoresist layer, and hardlyreaches the substrate. This means that any fine pattern is not obtainedfrom the prior art photoresist layer.

[0008] As described hereinbefore, the prior art products of photoresistare not available for the ArF excimer laser lithography, and thesemiconductor manufacturers desire a new product of photoresistavailable for the ArF excimer laser lithography. The structural unit ofthe photoresist is expected to exhibit large resistance against dryetching without the aromatic ring, because the photoresist would exhibitthe transparency to the ArF excimer laser light.

[0009] The prior art photoresist available for 193 nm ArF excimer laserlithography is taught by Takechi et. al., Journal of PhotopolymerScience and Technology, vol. 5, No. 3, pages 439 to 446, 1992. Thephotoresist is based on copolymer having adamantyl methacrylate unitswhich are alicylic polymer. Another prior art photoresist is based oncopolymer having isobornyl methacrylate units as disclosed by R. D.Allen et. al, Journal of Photopolymer Science and Technology, vol. 8,No. 4, pages 623 to 636, 1995 and vol. 9, No. 3, pages 465-474, 1996.Yet another prior art photoresist is based on co-polymer having thestructural unit of alternating copolymerization between norbornene andmaleic anhidride as taught by F. M. Houlihan et. al, Macromolecules,vol. 30, pages 6517-6524, 1997.

[0010] Carboxy group and hydroxy group are categorized in the polargroups. The polar group makes the photoresist strongly held in contactwith substrates, and are preferable to the photoresist. However, theaforementioned monomer, which has the alicylic group, does not have anypolar group. The prior art photoresist is hydrophobic, and thephotoresist layer is liable to peel off from the substrates such assilicon substrates. Thus, the first drawback inherent in the prior artphotoresist is the weak adhesion to substrates.

[0011] The second drawback inherent in the photoresist containing thepolymer having an alicylic group is poor uniformity of film formation.When the prior art photoresist is spread over substrates, the prior artphotoresist layers are irregular in thickness. This phenomenon is alsoderived from the hydrophobic property due to the lack of the polargroup.

[0012] The third drawback is a small difference in solubility betweenthe pre-exposure to light and the post-exposure. Adamantyl-containingresidue, isobornyl-containing residue and menthyl-containing residuegive the strong resistance against dry etching to the photoresist.However, the prior art photoresist does not have any residue which makesthe photoresist widely different in solubility between the pre-exposureto light and the post-exposure. This means that the photoresist layerhas a dull edge.

[0013] It is possible to overcome those drawbacks by employingcopolymerization with certain comonomers for improving the difference insolubility and/or comonomers for enhancing the adhesion to substrates.t-butyl methacrylate and tetrahydropyranyl methacrylate are examples ofthe comonomer for improving the difference in solubility, andmethacrylic acid is an example of the comonomer for enhancing theadhesion to substrates. However, the comonomer is required at least 50mole %. The comonomer is less resistive against dry etching. Thus, themanufacturers desire new photoresist which exhibits high transparency tothe exposure light, large difference in the solubility and strongadhesion to substrates without sacrifice of the resistance against dryetching.

[0014] The other sorts of photoresist, which contain the alternatingcopolymerization between norbornene and maleic anhydride, have thenorbornane ring. The norbornane ring also does not have any polar group,and the photoresist exhibits poor adhesion. When copolymer with acrylicacid is introduced into the resin based on the alternating copolymerbetween norbornene and maleic anhydride, the adhesion is improved.However, the resultant photoresist is less resistive against dryetching. The manufacturers also desire new photoresist exhibiting strongadhesion to substrates without sacrifice of the resistance against dryetching.

SUMMARY OF THE INVENTION

[0015] It is therefore an important object of the present invention toprovide photoresist which exhibits high transparency to light equal inwavelength to or less than 220 nm, large resistance against dry etchingand strong adhesion to substrates.

[0016] It is another important object of the present invention toprovide polymer to be used in the photoresist.

[0017] It is yet another important object of the present invention toprovide monomer to be used in the polymer.

[0018] It is still another important object of the present invention toprovide a method for transferring a pattern to the photoresist layer.

[0019] The present inventors found that 3-oxo-4-oxabicyclo [3.2.1]octane-2-yl skeleton was useful for photoresist. The present inventorsexamined documents referring to photoresist having the skeleton.Japanese Patent Application laid-open No. 2001-188351 taught thephotoresist having the bridged alicylic skeleton in which at least onering is lactone ring. Norbornyl monoene, norbornyl diene,tricyclodecamonoene, tricyclodecadiene, tetracyclodecamonoene andtetracyclodecadiene were written in the Japanese Patent Applicationlaid-open as the examples. Japanese Patent Application laid-open No.2000-26446 taught (meth)acrylate polymer having the bridged lactonestructure. However, the present inventors could not find any documentteaching that 3-oxo-4-oxabicyclo [3.2.1] octane-2-yl skeleton was usefulfor photoresist.

[0020] In accordance with one aspect of the present invention, there isprovided monomer for a chemically amplified photoresist comprising vinylmonomer having 3-oxo-4-oxabicyclo [3.2.1] octane-2-yl group expressed bygeneral formula (1)

[0021] where each of L¹, L², L³, L⁴, L⁵ and L⁶ is selected from thegroup consisting of hydrogen atom and alkyl groups having the carbonnumber from 1 to 8.

[0022] The hydrogen atom or alkyl group at L⁵ and the hydrogen atom oralkyl group at L⁶ may be replaced with alkylene groups having the carbonnumber 1 to 10 and bonded to each other for forming a ring.

[0023] The 3-oxo-4-oxabicyclo [3.2.1] octane-2-yl group expressed bygeneral formula (1) may be replaced with vinyl monomer with a bridgedalicylic δ lactone structure expressed by general formula (2)

[0024] where each of R² and R³ is selected from the group consisting ofhydrogen and alkyl groups having the carbon number from 1 to 4, each ofR⁴ to R⁶ is selected from the group consisting of hydrogen atom andmethyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groups eachhaving the carbon number from 1 to 10 and bonded for forming a ring andn is zero or 1.

[0025] In accordance with another aspect of the present invention, thereis provided polymer used for a chemically amplified photoresistcomprising vinyl polymer having 3-oxo-4-oxabicyclo [3.2.1] octane-2-ylgroup expressed by general formula (1)

[0026] where each of L¹, L², L³, L⁴, L⁵ and L⁶ is selected from thegroup consisting of hydrogen atom and alkyl groups having the carbonnumber from 1 to 8.

[0027] The hydrogen atom or alkyl group at L⁵ and the hydrogen atom oralkyl group at L⁶ may be replaced with alkylene groups having the carbonnumber 1 to 10 and bonded to each other for forming a ring.

[0028] The 3-oxo-4-oxabicyclo [3.2.1] octane-2-yl group expressed bygeneral formula (1) may be replaced with vinyl monomer with a bridgedalicylic δ lactone structure expressed by general formula (2)

[0029] where each of R² and R³ is selected from the group consisting ofhydrogen and alkyl groups having the carbon number from 1 to 4, each ofR⁴ to R⁶ is selected from the group consisting of hydrogen atom andmethyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groups eachhaving the carbon number from 1 to 10 and bonded for forming a ring andn is zero or 1.

[0030] In accordance with yet another aspect of the present invention,there is provided photoresist comprising polymer including vinyl polymerhaving 3-oxo-4-oxabicyclo [3.2.1] octane-2-yl group expressed by generalformula (1)

[0031] where each of L¹, L², L³, L⁴, L⁵ and L⁶ is selected from thegroup consisting of hydrogen atom and alkyl groups having the carbonnumber from 1 to 8, and photo-acid generator generating acid in thepresence of light equal in wave-length to or less than 220 nanometers;the ratio of the photo-acid generator to the photoresist is fallenwithin the range from 0.2% by mass to 30% by mass.

[0032] The hydrogen atom or alkyl group at L⁵ and the hydrogen atom oralkyl group at L⁶ may be replaced with alkylene groups having the carbonnumber 1 to 10 and bonded to each other for forming a ring.

[0033] The 3-oxo-4-oxabicyclo [3.2.1] octane-2-yl group expressed bygeneral formula (1) may be replaced with vinyl monomer with a bridgedalicylic δ lactone structure expressed by general formula (2)

[0034] where each of R² and R³ is selected from the group consisting ofhydrogen and alkyl groups having the carbon number from 1 to 4, each ofR⁴ to R⁶ is selected from the group consisting of hydrogen atom andmethyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groups eachhaving the carbon number from 1 to 10 and bonded for forming a ring andn is zero or 1.

[0035] In accordance with still another aspect of the present invention,there is provided a method for transferring a pattern to a photoresistlayer, comprising the steps of a) preparing a substrate and photoresistcomprising polymer including polymer having 3-oxo-4-oxabicyclo [3.2. 1]octane-2-yl group expressed by general formula (1)

[0036] where each of L¹, L², L³, L⁴, L⁵ and L⁶ is selected from thegroup consisting of hydrogen atom and alkyl groups having the carbonnumber from 1 to 8 and photo-acid generator generating acid in thepresence of light equal in wave-length to or less than 220 nanometers,the ratio of the photo-acid generator to the photoresist being fallenwithin the range from 0.2% by mass to 30% by mass, b) spreading thephotoresist on the substrate for forming a photoresist layer, c)exposing the photoresist layer to image-carrying light having awavelength between 180 nanometers and 220 nanometers for forming alatent image in the photoresist layer, and d) developing the latentimage so as to pattern the photoresist layer into a photoresistpatterned layer.

[0037] The hydrogen atom or alkyl group at L⁵ and the hydrogen atom oralkyl group at L⁶ may be replaced with alkylene groups having the carbonnumber 1 to 10 and bonded to each other for forming a ring.

[0038] The 3-oxo-4-oxabicyclo [3.2.1] octane-2-yl group expressed bygeneral formula (1) may be replaced with vinyl monomer with a bridgedalicylic δ lactone structure expressed by general formula (2)

[0039] where each of R² and R³ is selected from the group consisting ofhydrogen and alkyl groups having the carbon number from 1 to 4, each ofR⁴ to R⁶ is selected from the group consisting of hydrogen atom andmethyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groups eachhaving the carbon number from 1 to 10 and bonded for forming a ring andn is zero or 1.

[0040] The present inventors selected the 3-oxo-4-oxabicyclo [3.2.1]octane-2-yl skeleton from the bridged alicylic δ lactone skeletons forthe polymer used for chemically amplified photoresist according to thepresent invention. The 3-oxo-4-oxabicyclo [3.2.1] octane-2-yl skeletonenhanced the transparency of the chemically amplified photoresist to thelight equal in wavelength to or less than 220 nanometers withoutsacrifice of the resistance against etching and adhesion to substrates.The reasons for the preferable features were as follows.

[0041] First, the present inventors discovered that bicyclo [3.2.1]octane skeleton made the photoresist transparent to the light equal inwavelength to or less than 220 nanometers and resistive to dry etching.The reason for the high transparency was that the bridged alicylicstructure did not have any aromatic ring. The carbon density was so highthat the bridged alicylic structure well withstood the dry etching.Especially, the bicyclo [3.2.1] octane had the molecular structuredesirable from the viewpoint of the transparency and the resistanceagainst dry etching. The 3-oxo-4-oxabicyclo [3.2.1] octane-2-yl skeletonincluded the bicyclo [3.2.1.] octane skeleton so that the photoresistaccording to the present invention exhibited high transparency withoutsacrifice of the resistance against the dry etching.

[0042] Second, δ lactone ring had the dielectric constant larger invalue than that of the ester structure, ether structure and alcoholstructure. Referring to “CHEMICAL HANDBOOK basic II”, revised edition 3,pages 502 to 504, edited by Japanese Chemical Society and published byMaruzen Corporation, the dielectric constant of the compounds having thecarbon number 4 were as follows. The dielectric constant ofγ-buthyrolactone was 39, the dielectric constant of ethyl accetate was6.02, the dielectric constant of diethyl ether was 4.335, and thedielectric constant of 1-butanol was 17.51. Thus, the lactone structurewas larger in dielectric constant than the other structures. The largedielectric constant resulted in clear polarity. Especially, the δlactone exhibited an appropriate value of the dielectric constant. Thelarge dielectric constant was desirable for adhesion to substrates. The3-oxo-4-oxabicyclo [3.2.1] octane-2-yl skeleton had the δ lactone ringso that the photoresist according to the present invention achievedstrong adhesion to substrates.

[0043] The 3-oxo-4-oxabicyclo [3.2.1] octane-2-yl skeleton had both ofthe bicyclo [3.2.1] octane skeleton and the δ lactone skeleton. Thismeant that the 3-oxo-4-oxabicyclo [3.2.1] octane-2-yl skeleton wasexpected to exhibit synergism of the bicyclo [3.2.1] octane skeleton andthe δ lactone skeleton. Thus, the 3-oxo-4-oxabicyclo [3.2.1] octane-2-ylskeleton was desirable for the transparency to the light, resistanceagainst dry etching and strong adhesion to substrates.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] Monomer and Polymer

[0045] Any vinyl monomer is available for the chemically amplifiedphotoresist according to the present invention in so far as the vinylmonomer is active in polymerization. From this viewpoint, it ispreferable to use ethylene, a derivative of ethylene, vinyl chloride, aderivative of vinyl chloride, styrene, a derivative of styrene,acrylonitrile, a derivative of acrylonitrile, (meth)acrylate, aderivative of (meth)acrylate, norbornene carboxylic acid ester or aderivative of norbornene carboxylic acid ester for polymer. When thepolymer is produced from the ethylene, a derivative of ethylene, vinylchloride, a derivative of vinyl chloride, styrene, a derivative ofstyrene, acrylonitrile, a derivative of acrylonitrile, (meth)acrylate, aderivative of (meth)acrylate, norbornene carboxylic acid ester or aderivative of norbornene carboxylic acid ester, the vinyl polymer hasrepeated structural unit produced through the vinyl polymerization inthe principal chain

[0046] More particularly, it is preferable to use the derivatives of(meth)acrylate having the bridged alicylic δ lactone structure expressedby general formula (3) as the structural unit

[0047] where R¹ is selected from the group consisting of hydrogen atomand methyl group, each of R² and R³ is selected from the groupconsisting of hydrogen atom and alkyl groups having the carbon numbersfrom 1 to 4, each of R⁴, R⁵ and R⁶ is selected from the group consistingof hydrogen atom and methyl group, R⁷ and R⁸ are hydrogen atoms oralkylene groups having the carbon number from 1 to 10 and bonded to eachother for forming a ring and n is zero or 1.

[0048] When the derivative of (meth)acrylate is vinyl polymerized, theresultant polymer in the acrylic series has the bridged alicylic δlactone structure expressed by general formula (3′) in the principalchain as the repeated structural unit.

[0049] where R¹ is selected from the group consisting of hydrogen atomand methyl group, each of R² and R³ is selected from the groupconsisting of hydrogen atom and alkyl groups having the carbon numbersfrom 1 to 4, each of R⁴, R⁵ and R⁶ is selected from the group consistingof hydrogen atom and methyl group, R⁷ and R⁸ are hydrogen atoms oralkylene groups having the carbon number from 1 to 10 and bonded to eachother for forming a ring and n is zero or 1.

[0050] The derivatives of (meth)acrylate may have alicylic lactonestructure expressed by general formula (3″)

[0051] where R¹, R⁴, R⁵ and R⁶ are hydrogen atoms or methyl groups, R²and R³ are hydrogen atoms or alkyl groups having the carbon number from1 to 4 and R⁷ and R⁸ are hydrogen atoms or alkylene groups bonded toeach other for forming a ring. When the derivative of (meth)acrylatehaving the structural unit expressed by general formula (3″) ispolymerized, the resultant polymer has the structural unit expressed bygeneral formula (3″′) in the principal chain.

[0052] where R¹, R⁴, R⁵ and R⁶ are hydrogen atoms or methyl groups, R²and R³ are hydrogen atoms or alkyl groups having the carbon number from1 to 4 and R⁷ and R⁸ are hydrogen atoms or alkylene groups bonded toeach other for forming a ring. When chemically amplified resist isproduced on the basis of the polymer having the structural unitexpressed by the general formula (3″′), the chemically amplified resistcontains photo-acid generator. It is preferable that the polymer rangesfrom 70% to 99.8% by mass in the total mass of the polymer and thephoto-acid generator.

[0053] Derivatives of norbornene carboxylic acid ester are alsopreferable. The derivatives of norbornene carboxylic acid ester have abridged alicylic δ lactone structure expressed by general formula (4)

[0054] where R¹ is selected from the group consisting of hydrogen atomand methyl group, each of R² and R³ is selected from the groupconsisting of hydrogen atom and alkyl groups having the carbon numberfrom 1 to 4, each of R⁴, R⁵ and R⁶ is selected from the group consistingof hydrogen atom and methyl group, R⁷ and R⁸ are hydrogen atoms oralkylene groups having the carbon number from 1 to 10 and bonded to eachother for forming a ring and n is zero or 1.

[0055] When the derivative of norbornene carboxylic acid ester with thebridged alicylic δ lactone structure expressed by general formula (4) ispolymerized, the resultant polymer has a bridged alicylic δ lactonestructure expressed by general formula (4′) in the principal chain asthe repeated structural unit

[0056] where R¹ is selected from the group consisting of hydrogen atomand methyl group, each of R² and R³ is selected from the groupconsisting of hydrogen atom and alkyl groups having the carbon numberfrom 1 to 4, each of R⁴, R⁵ and R⁶ is selected from the group consistingof hydrogen atom and methyl group, R⁷ and R⁸ are hydrogen atoms oralkylene groups having the carbon number from 1 to 10 and bonded to eachother for forming a ring and n is zero or 1.

[0057] More than one vinyl monomer may be copolymerized. When more thanone vinyl monomer is copolymerized, the resultant copolymer has morethan one structural unit in the principal chain as the repeatedstructural unit. Thus, a wide variety of desirable properties are givento the photoresist according to the present invention by using thecopolymers.

[0058] As described hereinbefore, each of the R¹, R⁴, R⁵ and R⁶ is ahydrogen atom or methyl group in the general formulae (2), (3), (4),(3′) and (4′). In those general formulae, each of the R² and R³ is ahydrogen atom or alkyl group having the carbon number from 1 to 4, i.e.,methyl group, ethyl group, n-propyl group and n-butyl. R⁷ and R⁸ arehydrogen atoms or alkylene groups, which have the carbon number from 1to 10 and are bonded to each other for forming a ring. Examples arepropylene group [—(CH₂)₃—], butylene group [—(CH₂) ₄—] and1,3-cyclopentylene group.

[0059] In the general formula (1), L¹ is exchangeable for R⁴, L² isexchangeable for R⁵, L³ and L⁴ are independently exchangeable for R⁶, L⁵is exchangeable for R⁷, and L⁶ is exchangeable for R⁸.

[0060] For examples, in case where the derivatives of (meth)acrylatehave n equal to 1, following compounds are available for the polymerand, accordingly, photoresist.

[0061] In case where the derivatives of norbornene carboxylic acid esterhave n equal to 1, following compounds are available for the polymerand, accordingly, the photoresist.

[0062] In case where the derivatives of (meth)acrylate have n equal tozero, following compounds are available for the polymer and photoresist.

[0063] In case where the derivatives of norbornene carboxylic acid esterhave n equal to zero, followings are available for the polymer and thephotoresist.

[0064] In addition to the above-described repeated structural unit,comonomer may be copolymerized so as to introduce a repeated structuralunit to be decomposed by acid produced from photo-acid generator and/oranother repeated structural unit expected to impart various desirablefeatures into the polymer.

[0065] The repeated structural units, which are produced from thecomonomer, are expected to exhibit a high decomposition efficiency,impart desirable features to the polymer and have good affinity to thevinyl polymerization. From these viewpoints, it is desirable to have atleast one of the structural units expressed by the general formulae(3′a), (3′b) and (3′c).

[0066] where R⁹ is selected from the group consisting of hydrogen atomand methyl group, R¹⁰ is selected from the group consisting of groups tobe decomposed by acid and bridged cyclic hydrocarbon groups having thecarbon number from 7 to 13 and having groups to be decomposed by acid,R¹¹ is selected from the group consisting of hydrogen atom and methylgroup, R¹² is selected from the group consisting of hydrogen atom,hydrocarbon groups having the carbon number from 1 to 12, bridged cyclichydrocarbon groups having the carbon number from 7 to 13 and eitherhydroxy or carboxy group and 2,6-norbornanecarbolactone-5-yl group and Mis selected from the group consisting of hydrogen atom, hydroxy group,hydroxyalkyl groups and acid dissociated organic groups having thecarbon number equal to or less than 20 and to be decomposed by acid forproducing carboxy group.

[0067] R¹⁰ is the group to be decomposed by acid or the bridged cyclichydrocarbon groups, which have the carbon number from 7 to 13 and agroup to be decomposed by acid. Examples of the group to be decomposedby acid are t-butyl, tetrahydropyran-2-yl group, tetrahydrofuran-2-ylgroup, 4-methoxytetrahydropyran-4-yl group, 1-ethoxyethyl group,1-butoxyethyl group, 1-propoxyethyl group, 3-oxocyclohexyl group,2-methyl-2-adamantyl-group, 2-ethyl-2-adamantyl group,1-methyl-1-adamantylethyl group, 8-methyl-8-tricyclo [5. 2. 1. 0^(2, 6)]decyl group, 1,2,7,7-tetramethyl-2-norbornyl group, 2-acetoxymentylgroup, 2-hydroxymentyl group and 1-methyl-1-cyclohexylethyl group.

[0068] Examples of the bridged cyclic hydrocarbon groups having thecarbon number from 7 to 13 and a group to be decomposed by acid haveester group, and are tricyclo [5. 2. 1. 0^(2, 6)] decyl methyl group,tricyclo [5. 2. 1. 0^(2, 6)] decyl group, adamantyl group, norbornylgroup, methylnorbornyl group, isobornyl group, tetracyclo [4. 4. 0.1^(2, 5). 1^(7, 10)] dodecyl group and methyltetracyclo [4. 4. 0. 1² ⁵.1^(7, 10)] dodecyl group. The chemical structures of these groups are asfollows. tricyclo [5. 2. 1. 0^(2,6)] decyl methyl group with estergroup,

tricyclo [5. 2. 1. 0^(2,6)] decyl group with ester group,

adamantyl group, with ester group,

norbornyl group with ester group,

methylnorbornyl group with ester group,

isobornyl group with ester group,

tetracyclo [4. 4. 0. 1^(2,5). 1^(7,10)] dodecyl group with ester group,

methyltetracyclo [4. 4. 0. 1^(2,5). 1^(7,10)] dodecyl group with estergroup,

[0069] In the chemical structures, R¹⁷ is the group to be decomposed byacid, and examples of the group are t-butyl, tetrahydropyran-2-yl group,tetrahydrofuran-2-yl group, 4-methoxytetrahydropyran-4-yl group,I-ethoxyethyl group, 1-butoxyethyl group, 1-propoxyethyl group,3-oxocyclohexyl group, 2-methyl-2-adamantyl group, 2-ethyl-2-adamantylgroup, 8-methyl-8-tricyclo [5. 2. 1. 0^(2, 6)] decyl group,1,2,7,7-tetramethyl-2-norbornyl group, 2-acetoxymenthyl group,2-hydroxymenthyl group and 1-methyl-1-cyclohexylethyl group.

[0070] In case where R¹² is a hydrocarbon group having the carbon numberfrom 1 to 12, examples of R¹² are methyl group, ethyl group, n-propylgroup, isopropyl group, n-butyl group, isobutyl group, t-butyl group,cyclohexyl group, tri-cyclo [5. 2. 1. 0^(2. 6)] decyl group, adamantylgroup, norbornyl group, isobornyl group and tetracyclo [4. 4. 0.1^(2, 5). 1 ^(7, 10)] dodecyl group.

[0071] Examples of the bridged cyclic hydrocarbon having the carbonnumber from 7 to 13 and one of the hydroxy group and carboxy group arehydroxyadamantyl group, dihydroxyadamantyl group, hydroxynorbornylgroup, hydroxytetracyclododecyl group, carboxyadamantyl group,carboxynorbornyl group and carboxytetracyclododecyl group.

[0072] In case where M is hydroxyalkyl group, examples of M arehydroxymethyl group and hydroxyethyl group.

[0073] In case where M is the acid dissociated organic group having thecarbon number equal to or less than 20 and to be decomposed by acid forproducing carboxy group, examples of M are t-butoxycarbonyl group,tetrahydropyranyloxycarbonyl group, tetrahydrofuranyloxycarbonyl group,4-methoxy tetorahydropyranyloxycarbonyl group, 1-ethoxyethoxycarbonylgroup, 1-butoxyethoxycarbonyl group, 1-propoxyethoxycarbonyl group,3-oxocyclohexyloxycarbonyl group, 2-methyl-2-adamantyloxycarbonyl group,2-ethyl-2-adamantyloxycarbonyl group, 8-methyl-8-tricyclo [5. 2. 1.0^(2, 6)] decyloxycarbonyl group,1,2,7,7-tetramethyl-2-norbornyloxycarbonyl group,2-acetoxymenthyloxycarbonyl group, 2-hydroxymenthyloxycarbonyl group and1-methyl-1-cyclohexylethoxycarbonyl group.

[0074] Other repeated structural units are expected to enhance thedecomposition efficiency and/or give the photoresist other desirablefeatures. Comonomers for these repeated structural units are to be wellpolymerized for producing vinyl polymer. From this viewpoint, at leastone of the structural units expressed by the general formulae (4′a),(4′b) and (4′c) is preferable.

[0075] where R¹³ is selected from the group consisting of hydrogen atomand methyl group, R¹⁴ is selected from the group consisting of hydroxygroup, hydroxyalkyl group and acid dissociated organic groups having thecarbon number equal to or less than 20 and to be decomposed by acid forproducing carboxy group, R¹⁵ is selected from the group consisting ofhydrogen atom and methyl group and R¹⁶ is selected from the groupconsisting of hydroxy group, hydroxyalkyl group and acid dissociatedorganic groups having the carbon number equal to or less than 20 and tobe decomposed by acid for producing carboxy group.

[0076] Each of R¹⁴ and R¹⁶ is hydroxy group, hydroxyalkyl group such ashydroxymethyl group and hydroxyethyl group or acid dissociated organicgroups having the carbon number equal to or less than 20 and to bedecomposed by acid for producing carboxy group. The group of aciddissociated organic groups contains t-butoxycarbonyl group,tetrahydropyranyloxycarbonyl group, tetrahydrofuranyloxycarbonyl group,4-methoxytetrahydropyranyloxycarbonyl group, 1-ethoxyethoxycarbonylgroup, 1-butoxyethoxycarbonyl group, 1-propoxyethoxycarbonyl group,3-oxocyclohyxyloxycarbonyl group, 2-methyl-2-adamantyloxycarbonyl group,2-ethyl-2-adamantyloxycarbonyl group, 8-methyl-8-tricyclo [5. 2. 1.0^(2, 6)] decyloxycarbonyl group,1,2,7,7-tetramethyl-2-norbornyloxycarbonyl group,2-acetoxymenthyloxycarbonyl group, 2-hydroxymenthyloxycarbonyl group and1-methyl-i-cyclohexylethoxycarbonyl group.

[0077] From the viewpoint of desirable properties of resultantcopolymer, it is preferable to copolymerize each of the repeatedstructural units expressed by the general formulae (3′a), (3′b) and(3′c) with at least one of the repeated structural unit expressed by thegeneral formulae (4′a), (4′b) and (4′c). It is also preferable tocopolymerize each of the repeated structural units expressed by thegeneral formulae (4′a), (4′b) and (4′c) with at least one of therepeated structural unit expressed by the general formulae (3′a), (3′b)and (3′c). The repeated structural units expressed by the generalformulae (3′a) to (3′c) may be selectively incorporated in the polymerconcurrently with the repeated structural units expressed by the generalformulae (4′a) to (4′c) so as to give a wide variety of desirableproperties to the polymer.

[0078] It is preferable that the copolymer contains at least one of therepeated structural units expressed by the general formulae (3′) and(4′) fallen within the range between 5 mole % and 90 mole % from theviewpoint of the properties of the resultant polymer It is morepreferable that at least one of the repeated structural units expressedby the general formulae (3′) and (4′) is fallen within the range between7 mole % and 80 mole %. It is much more preferable that at least one ofthe repeated structural units expressed by the general formulae (3′) and(4′) is fallen within the range between 10 mole % and 70 mole %.

[0079] Since the repeated structural units expressed by the generalformulae (3′a) to (3′c) well react with the derivatives of(meth)acrylate expressed by the general formula (3), it is preferable tomake the repeated structural unit or units expressed by the generalformulae (3′a) to (3′c) copolymerized with the repeated structural unitexpressed by the general formula (3′). In this instance, it ispreferable that the structural unit expressed by general formula (3′) isfallen within the range between 5 mole % and 90 mole % of the copolymer.It is more preferable that the structural unit expressed by generalformula (3′) is fallen within the range between 7 mole % and 80 mole %of the copolymer. It is much more preferable that the structural unitexpressed by general formula (3′) is fallen within the range between 10mole % and 70 mole % of the co-polymer Since the repeated structuralunits expressed by the general formulae (4′a) to (4′c) well react withthe derivatives of norbornene carboxylic acid ester expressed by thegeneral formula (4), it is preferable to make the repeated structuralunit or units expressed by the general formulae (4′a) to (4′c)copolymerized with the repeated structural unit expressed by the generalformula (4′). In this instance, it is preferable that the structuralunit expressed by general formula (4′) is fallen within the rangebetween 5 mole % and 90 mole % of the copolymer. It is more preferablethat the structural unit expressed by general formula (4′) is fallenwithin the range between 7 mole % and 80 mole % of the copolymer. It ismuch more preferable that the structural unit expressed by generalformula (4′) is fallen within the range between 10 mole % and 70 mole %of the copolymer.

[0080] The polymers described hereinbefore are produced through a usualpolymerization process such as, for example, the radical polymerization,anionic polymerization or addition polymerization. A suitablepolymerization initiator such as, for example, azobisisobutyronitrile(AIBN) is, by way of example, added to dry tetrahydrofuran in inertatmosphere such as argon or nitrogen, and the polymerization initiatorand the dry tetrahydrofuran are agitated at 50 degrees to 70 degrees incentigrade for 0.5 hour to 12 hours. Then, the polymer is producedthrough the radical polymerization.

[0081] In case where the polymer is produced through the additionpolymerization, the polymer may be produced through the processdisclosed by J. P. Mathew, Macromolecules, vol. 29, pages 2755 to 2763,1996. Namely, suitable catalyst in palladium compound series is used inthe addition polymerization. (η³-allyl) Pd(BF₄), (η³-allyl) Pd (SbF₆)and [Pd (CH₃CN)₄] (BF₄)₂ are examples of the palladium compoundcatalyst. Otherwise, nickel compound catalyst such as bis(pentafluorophenyl) nickel toluene complex is used in the additionpolymerization as taught by T. Chiba et. al, Journal of PhotopolymerScience and Technology, vol. 13, No. 4, pages 657 to 664, 2000.

[0082] The weight average molecular weight of the polymer available forthe photoresist according to the present invention is fallen within therange from 2,000 to 200,000.

[0083] Chemically Amplified Resist

[0084] Chemically amplified resist embodying the present inventioncontains at least the polymer described hereinbefore and photo-acidgenerator. In case where n and both of R² and R³ are 1 and alkyl groupin the structural unit expressed by the general formula (3′), thealicylic lactone unit is a tertiary ester of carboxylic acid, and iseliminated in the presence of acid. Thus, it is an acid decomposedgroup. The reaction is as follows.

[0085] It is preferable that the photo-acid generator generates acid inthe presence of the light equal in wavelength to or less than 400nanometers. It is more preferable to produce the acid in the presence ofthe light having the wave-length between 180 nanometers and 220nanometers. There is not any limit to the photo-acid generator in so faras liquid mixture, in which the mixture containing the photo-acidgenerator and the polymer such as the polymer in acrylic series is welldissolved in organic solvent, is uniformly spread by using a spincoater, by way of example. More than one photo-acid generator may bemixed with the polymer.

[0086] Examples of the photo-acid generator are derivatives oftriphenylsulfonium salt, derivatives of diphenyliodonium salt,derivatives of dialkylphenacylsulfonium salt, derivatives ofnitrobenzylsulfonate and derivatives of sulfonic acid ester ofN-hydroxysuccinimide.

[0087] Another photo-acid generator is disclosed by J. V. Crivello et.al, Journal of the Organic Chemistry, vol. 43, No. 15, pages 3055 to3058, 1978. J. V. Crivello et. al. teach derivatives oftriphenylsulfonium salt and other onium salts such as sulfonium salt,iodonium salt, phosphonium salt, diazonium salt and ammonium salt. Yetanother photo-acid generator is disclosed by O. Nalamasu et. al, SPIEProceedings, vol. 1262, page 32, 1990. O. Nalamasu et. al. teach2,6-dinitrobenzyl esters. Still another photo-acid generator isdisclosed by Takumi Ueno et. al, Proceedings of PME′ 89, Kohdansha,pages 413 to 424, 1990, and Ueno et. al. teach 1,2,3-tri(methanesulfonyloxy) benzen. Yet another photo-acid generator isdisclosed in Japanese Patent Application laid-open No. 5-134416, and issulfosuccinimide.

[0088] From the viewpoint that the photo-acid generator makes thechemically amplified resist well sensitive to the exposure light forproducing a fine latent image therein, it is preferable that the contentof the photo-acid generator is equal to or greater than 0.2% by mass ofboth polymer and photo-acid generator. It is more preferable that thechemically amplified resist contains the photo-acid generator equal toor greater than 1% by mass of both polymer and photo-acid generator.However, if the content of photo-acid generator is greater than 30% bymass, the chemically amplified resist is less liable to be uniformlyspread, and the scum is not ignorable after the development Thus, theupper limit of the content is 30% by mass. It is more preferable thatthe content of the photo-acid generator is equal to or less than 15% bymass. Thus, the photo-acid generator is to range from 0.2% by mass to30% by mass, and the more preferable range is between 1% by mass and 15%by mass.

[0089] When the manufacturer prepares the chemically amplified resist,appropriate solvent is used. Any organic solvent is available for thechemically amplified resist in so far as the polymer and the photo-acidgenerator are well dissolved therein for being uniformly spread oversubstrates. Only one sort of solvent or more than one sort of solvent isused for preparing the chemically amplified resist according to thepresent invention.

[0090] Examples of the solvent are n-propyl alcohol, iso-propyl alcohol,n-butyl alcohol, tert-butyl alcohol, propylene glycol monomethyletheracetate, propylene glycol monoethylether acetate, methyl cellosolveacetate, ethyl cellosolve acetate, ethyl lactate, methyl lactate,2-methoxybutyl acetate, 2-ethoxyethyl acetate, methyl, pyruvate, ethylpyruvate, 3-methoxy methyl propionate, 3-methoxy ethyl propionate,N-methyl-2-pyrrolidinone, cyclohexanone, cyclopentanone, cyclohexanol,methyl ethyl ketone, 1,4-dioxane, ethyleneglycolmonomethylether,ethyleneglycolmonomethylether acetate, ethyleneglycolmonoethylether,ethyleneglycolmonoisopropylether, diethyleneglycolmonomethylether anddiethyleneglicoldimethylether.

[0091] The chemically amplified resist according to the presentinvention may further contain other additives such as, for example,dissolution inhibitor, organic base, surface active agent, dyestuff,stabilizer, coating property improving agent and coloring agent.

[0092] Pattern Transfer

[0093] A pattern image is transferred from a photo-mask to a chemicallyamplified resist layer as follows. First, the chemically amplifiedresist described hereinbefore is prepared. The chemically amplifiedresist solution is spread over a layer such as, for example, asemiconductor wafer or a semiconductor/insulating layer on thesemiconductor wafer. A spin coater may be used for spreading thechemically amplified resist solution.

[0094] Subsequently, the chemically amplified resist layer is pre-baked,and, thereafter, the semiconductor wafer is inserted into a chamber ofan aligner. The aligner is well known to skilled person, and no furtherdescription is hereinbelow incorporated. Laser light is radiated from alight source to a photo-mask. The laser light has the wavelength between1 80 nanometers and 220 nanometers. In this instance, the light sourceradiates 193 nanometer wavelength ArF excimer laser light. The ArFexcimer laser light passes through the photo-mask, and carries thepattern image on the photo-mask. The image-carrying light reaches thechemically amplified resist layer. The image-carrying light produces alatent image in the chemically amplified resist layer.

[0095] The semiconductor wafer is taken out from the aligner, and thelatent image is developed. Then, the chemically amplified resist layeris patterned into a resist mask. Using the resist mask, thesemiconductor/insulating layer is, by way of example, selectivelyetched. Otherwise, dopant impurity may be ion implanted into thesemiconductor/insulting layer or semiconductor wafer. Thus, thesemiconductor device manufactures form miniature patterns on or over thesemiconductor wafers.

[0096] Description is hereinbelow made on several examples. However,these examples do not set any limit to the scope of the presentinvention. High-purity reagents and other chemicals used in the exampleswere purchased in the market. However, when special reagent or chemicalwas used, the special reagent/chemical is detailed.

FIRST EXAMPLE

[0097] The present inventors synthesized methacrylate, i.e.,Methacrylate 1 through the following reaction formula.

[0098] The methacrylate, ire., Methacrylate 1 was expressed by thegeneral formula (3) where R¹, R² and R³ were methyl groups, R⁴, R⁵ andR⁶ were hydrogen atoms, R⁷ and R⁸ were propylene groups, i.e.,[—(CH₂)₃—] bonded to each other for forming a ring and n was 1.

[0099] In detail, 25.4 grams of tricyclodecane-8-one was dissolved in150 milliliters of methylene chloride, and 42.6 grams of sodium hydrogencarbonate was added to the resultant solution. 50 grams ofm-chloroperbenzoic acid dissolved in 400 milliliters of methylenechloride was further dropped into the resultant solution. The resultantsolution was agitated all night at room temperature. Then, sodiumm-chlorobenzoate acid was deposited, and was filtrated. The filtrate waswashed in 5% water solution of sodium sulfite, thereafter, in 5% watersolution of sodium carbonate and, finally, in brine. The organic layerwas dried with MgSO₄, and methylene chloride was eliminated in vacuumtherefrom. The residue was distilled in vacuum, i.e., 0.35 mm Hg at 110degrees to 111 degrees in centigrade. Then, 24.8 grams of lactone 1 wasobtained. The yield was 88%.

[0100] Subsequently, 140 milliliters of dry THF was cooled to −78degrees in centigrade, and 70 milliliters of 2 mole/1 THF solution oflithium dilsopropyl amide was dropped thereinto in argon atmosphere. 10grams of the lactone compound, i.e., Lactone 1, was dissolved in 20milliliters of dry THF, and the resultant solution was further droppedthereinto. Reaction proceeded for an hour at −78 degrees in centigrade,and 26.6 grains of acetone was dropped thereinto. The resultant solutionwas agitated for 4 hours, and 10% hydrochloric acid water solution wasadded to the resultant solution until the solution was changed to acid.An organic layer was extracted from the solution by using 300milliliters of ethyl acetate. The organic layer was washed in 5% ofsodium hydrogen carbonate and, thereafter, in brine. After the washing,the organic layer was dried with magnesium sulfate, and the solvent waseliminated in vacuum. Hexane was added to the residue, and, thereafter,cooled. Then, a piece of crystal was precipitated, and was filtered.6.04 grams of alcohol compound, i.e., Alcohol 1 was obtained. The yieldwas 24%.

[0101] 7 grams of alcohol, 3.79 grams of triethylamine and 9 milligramof phenothiazine were dissolved in 30 milliliters of dry methylenechloride, and solution, in which 3.26 grams of methacryloyl chloride wasdissolved in 5 milliliters of dry methylane chloride, was dropped intothe resultant solution cooled with ice. The resultant solution wascontinuously cooled with ice for 3 hours, and, thereafter, was agitatedthrough all night at room temperature.

[0102] Subsequently, 200 milliliters of ethyl acetate was added, and anorganic layer was obtained. The organic layer was washed in 0.5 Nhydrochloric acid, thereafter, in 3% water solution of sodium hydrogencarbonate and, finally, in brine. The organic layer was dried withmagnesium sulfate, and the solvent was eliminated in vacuum. The residuewas separated and refined through a silica gel column. Elute containedhexane and ethyl acetate at 5:1. 2.4 grams of methacrylate, i.e.,Methacrylate 1 was obtained. The yield was 26%.

[0103] The methacrylate was analyzed. The result of ¹H-NMR (CDCl₃) wasas follows; δ was 0.84 to 1.0 (1H, m), 1.0 to 1.13 (1H, m), 1.66 (3H,s), 1.78 (3H, s), 1.91 (3H, s), 1.27 to 1.41 (1H, m), 1.67 to 1.75 (2H,m), 1.94 to 2.13 (3H, m), 2.25 to 2.41 (2H, m), 2.75 (1H, q), 3.06 (1H,s), 4.49 (1H, s), 5.54 (1H, s) and 6.04 (1H, s).

[0104] The result of 1R (KBr) was as follows; 2850, 2950 (νC—H), 1712,1728 (νC═O), 1632 (νC═C) and 1136, 1184 (νC—O) cm⁻¹.

SECOND EXAMPLE

[0105] The present inventors synthesized acrylate expressed as follows.

[0106] The acrylate was expressed by the general formula (3) where whereR¹, R⁴, R⁵ and R⁶ were hydrogen atoms, R² and R³ were methyl groups, R⁷and R⁸ were propylene groups, i.e., [—(CH₂)₃—] bonded to each other forforming a ring and n was 1.

[0107] The acrylate was synthesized as similar to the synthesis of themethacrylate except that the methacryloyl chloride was replaced withacryloyl chloride. The yield was 21%.

[0108] The acrylate was analyzed. The result of ¹H-NMR (CDCl₃) was asfollows; δ was 0.87 to 1.12 (2H, m), 1.24 to 1.42 (1H, m), 1.62 (3H, s),1.78 s), 1.65 to 1.77 (2H, m), 1.90 to 2.11 (2H, m), 2.26 to 2.41 (3H,m), 2.75 (1H, q), 3.17 (1H, s), 4.48 (1H, s), 5.58 (1H, d), 6.03 (1H,dd) and 6.34 (1H, d).

[0109] The result of 1R (KBr) was as follows; 2850, 2950 (νC—H), 1720(νC═O), 1616, 1632 (νC═C) and 1140, 1192 (νC—O) cm⁻¹.

THIRD EXAMPLE

[0110] The present inventors further synthesized acrylate, i.e.,Acrylate 1 through the following reaction formula.

[0111] The acrylate, i.e., Acrylate 1 was expressed by the generalformula (3) where R¹, R², R³, R⁴, R⁵ and R⁶ were hydrogen atoms, R⁷ andR⁸ were propylene groups, i.e., [—(CH₂)₃—] bonded to each other forforming a ring and n was 1.

[0112] The synthesis for the acrylate was similar to that for the firstexample except that the acetone was replaced with formaldehyde in thesynthesis of the alcohol compound, i.e., Alcohol 2 and that themethacryloyl chloride was replaced with acryloyl chloride. The yield was18%.

[0113] The acrylate was analyzed. The result of ¹H-NMR (CDCl₃) was asfollows; δ was 0.88 to 1.19 (2H, m), 1.28 to 1.43 (1H, m), 1.56 to 1.85(2H, m), 1.93 to 2.11 (3H, m), 2.16 to 2.22 (1H, m), 2.34 to 2.45 (1H,m), 2.69 to 2.87 (2H, m), 4.44 (1H, d), 4.46 (1H, d), 4.51 (1H, s), 5.88(1H, d), 6.14 (1H, dd) and 6.44 (1H, d).

[0114] The result of 1R (KBr) was as follows; 2866, 2954 (νC—H), 1732(νC═O), 1635 (νC═C) and 1189 (νC—O) cm⁻¹.

FOURTH EXAMPLE

[0115] The present inventors synthesized polymer, which contained astructural unit expressed by the general formula (3′) at 50 mole % andanother structural unit expressed by the general formula (3′b) at 50mole %. These structural units were as follows.

[0116] The first structural unit was expressed by the general formula(3′) where R¹, R² and R³ were methyl groups, R⁴, R⁵ and R⁶ were hydrogenatoms, R⁷ and R⁸ were propylene groups, i.e., [—(CH₂)₃—] bonded to eachother for forming a ring and n was 1. The second structural unit wasexpressed by the general formula (3′b) where R¹¹ was methyl group andR¹² was 2,6-norbornanecarbolactone-5-yl group.

[0117] The synthesis proceeded as follows. 2.4 grams of methacrylate,which was obtained through the synthesis for the first example, and 1.82grams of 5-methacryloyloxy-2,6-norbornanecarbolacione were dissolved in22 milliliters of dry tetrahydrofuran in a 100 ml flask. 108 milligramsof AIBN was added thereto, and was agitated in argon atmosphere at 60degrees to 65 degrees in centigrade. After 3 hours, the solution wascooled, and the reactant mixture was poured into 400 milliliters ofmethanol. Deposited precipitate was filtrated. The filtrate was refined,gain. Thus, 2.95 grams of the polymer was obtained. The yield was 70%.

[0118] The polymer was analyzed. The copolymerization ratio was 50:50 onthe basis of the integral ratio of ¹H-NMR. From the result of GPCanalysis, weight average molecular weight (Mw) was 9600 (polystyrene),and the degree of dispersion (Mw/Mn) was 1.83.

FIFTH EXAMPLE AND SIXTH EXAMPLE

[0119] The fifth and sixth examples were polymerized as similar to thefourth example except for the ratio of the monomers as shown in thefollowing table. Copolymeri- Ratio of zation Ratio Weight AverageMonomers (by mole) Molecular Weight Fifth Example 0.3/0.7 0.31/0.69 8500 Sixth Example 0.7/0.3 0.7/0.3 10800

SEVENTH EXAMPLE AND EIGHTH EXAMPLE

[0120] The seventh and eighth examples were polymerized as similar tothe fourth example except for the amount of AIBN, i.e., concentration.AIBN concentration, copolymerization ratio and weight average molecularweight were as follows. Copolymeri- AIBN zation Ratio Weight AverageConcentration (by mole) Molecular Weight Seventh Example 0.5 mole %0.5/0.5 45000 Eighth Example  10 mole % 0.49/0.51  4100

NINTH EXAMPLE

[0121] The present inventors synthesized polymer in acrylic series. Thepolymer contained a structural unit expressed by the general formula(3′) at 50 mole % and another structural unit expressed by the generalformula (3′a) at 50 mole %. These structural units were as follows.

[0122] The first structural unit was expressed by the general formula(3′) where R¹, R², R³, R⁴, R⁵ and R⁶ were hydrogen atoms, R⁷ and R⁸ werepropylene groups, i.e., [—(CH₂)₃—] bonded to each other for forming aring and n was 1. The second structural unit was expressed by thegeneral formula (3′a) where R⁹ was hydrogen atom and R¹⁰ wast-butoxycarbonyltetracyclododecyl group.

[0123] The synthesis was similar to that for the fourth example exceptthat the present inventors used the monomer of the third example andt-buthoxycarbonyl-tetracyclododecyl acrylate instead of the monomer ofthe first example and 5-methacryloyloxy-2,6-norbornanecarbolactone. Theyield was 54%, and the weight average molecular weight Mw was 10800. Thedegree of dispersion Mw/Mn was 1.84.

TENTH EXAMPLE

[0124] The present inventors synthesized polymer in acrylic series. Thepolymer contained a structural unit expressed by the general formula(3′) at 50 mole % and another structural unit expressed by the generalformula (3′a) at 50 mole %. These structural units were as follows.

[0125] The first structural unit was expressed by the general formula(3′) where R¹, R², R³, R⁴, R⁵ and R⁶ were hydrogen atoms, R⁷ and R⁸ werepropylene groups, i.e., [—(CH₂)₃—] bonded to each other for forming aring and n was 1. The second structural unit was expressed by thegeneral formula (3′a) where R⁹ was hydrogen atom and R¹⁰ was2-methyl-2-adamantyl group.

[0126] The synthesis was similar to that for the ninth example exceptthat the present inventors used 2-methyl-2-adamantyl acrylate instead oft-butoxycarbonyltetracyclododecyl acrylate. The yield was 51%, and theweight average molecular weight Mw was 9100. The degree of dispersionMw/Mn was 1.92.

ELEVENTH EXAMPLE

[0127] The present inventors synthesized polymer in acrylic series. Thepolymer contained a structural unit expressed by the general formula(3′) at 30 mole %, another structural unit expressed by the generalformula (3′a) at 50 mole % and yet another structural unit expressed bythe general formula (3′b) at 20 mole %. These structural units were asfollows.

[0128] The first structural unit was expressed by the general formula(3′) where R¹, R², R³, R⁴, R⁵ and R⁶ were hydrogen atoms, R⁷ and R⁸ werepropylene groups, i.e., [—(CH₂)₃—] bonded to each other for forming aring and n was 1. The second structural unit was expressed by thegeneral formula (3′a) where R⁹ was hydrogen atom and R¹⁰ wast-butoxycarbonyltetracyclododecyl group. The third structural unit wasexpressed by the general formula (3′b) where R¹¹ was hydrogen atom andR¹² was 2,6-norbornanecarbolactone-5-yl group.

[0129] The synthesis was similar to that for the fourth example. In thesynthesis, the monomer of the third example,t-butoxycarbonyltetracyclododecyl acrylate and5-acryloyloxy-2,6-norbornanecarbolactone were used. The yield was 57%,and the weight average molecular weight Mw was 8700. The degree ofdispersion Mw/Mn was 1.76.

TWELFTH EXAMPLE

[0130] The present inventors synthesized polymer in acrylic series. Thepolymer contained a structural unit expressed by the general formula(3′) at 30 mole %, another structural unit expressed by the generalformula (3′a) at 50 mole % and yet another structural unit expressed bythe general formula (3′b) at 20 mole %. These structural units were asfollows.

[0131] The first structural unit was expressed by the general formula(3′) where R¹, R², R³, R⁴, R⁵ and R⁶ were hydrogen atoms, R⁷ and R⁸ werepropylene groups, i.e., [—(CH₂)₃—] bonded to each other for forming aring and n was 1. The second structural unit was expressed by thegeneral formula (3′a) where R⁹ was hydrogen atom and R¹⁰ wast-butoxycarbonyltetracyclododecyl group. The third structural unit wasexpressed by the general formula (3′b) where R¹¹ was methyl group andR¹² was 3-hydroxy-1-adamantyl group.

[0132] The synthesis was similar to that for the fourth example. In thesynthesis, the monomer of the third example,t-butoxycarbonyltetracyclododecyl acrylate and3-hydroxy-1-adamantylmethacrylate were used. The yield was 48%, and theweight average molecular weight Mw was 10500. The degree of dispersionMw/Mn was 2.02.

THIRTEENTH EXAMPLE

[0133] The present inventors synthesized polymer in acrylic series Thepolymer contained a structural unit expressed by the general formula(3′) at 50 mole % and another structural unit expressed by the generalformula (3′c) at 50 mole %. These structural units were as follows.

[0134] The first structural unit was expressed by the general formula(3′) where R¹, R² and R³ were methyl groups, R⁴, R⁵ and R⁶ were hydrogenatoms, R⁷ and R⁸ were propylene groups, i.e., [—(CH₂)₃—] bonded to eachother for forming a ring and n was 1. The second structural unit wasexpressed by the general formula (3′c) where M was hydrogen atom.

[0135] The synthesis was similar to that for the fourth example. In thesynthesis, the monomer of the first example, norbornene and maleicanhidride were used. The yield was 26%, and the weight average molecularweight Mw was 5600. The degree of dispersion Mw/Mn was 2.24.

FOURTEENTH EXAMPLE

[0136] The present inventor synthesized a derivative of norborneneexpressed as follows.

[0137] The derivative of norbornene was expressed by the general formula(4)

[0138] where R¹, R², R³, R⁴, R⁵ and R⁶ were hydrogen atoms, R⁷ and R⁸were propylene groups, i.e., [—(CH₂)₃—] bonded to each other for forminga ring and n was 1.

[0139] The derivative was synthesized as follows. 20 grams of thederivative of acrylate obtained as the third example was dissolved in 20milliliters of toluene. 7 grams of cyclopentadiene was dropped into thesolution cooled with ice, and was agitated through all night.Dicyclopentadiene was produced as by-product, and was eliminated invacuum. Then, 24.9 grams of the derivative of norbornene was obtained.The derivative of norbornene was viscous liquid, and the yield was 95%.

[0140] The derivative of norbornene was analyzed. The result of ¹H-NMR(CDCl₃) was as follows; δ was 0.84 to 1.17 (2H,m), 1.19 to 1.53 (4H, m),1.65 to 2.45 (8H, m), 2.64 to 3.3 (4H, m), 4.16 to 4.4 (2H, m), 4.5 (1H,s), 5.8 to 5.98 (1H, m) and 6.1 to 6.3 (1H, m). The result of 1R(KBr)was as follows; 2951, 2866 (νC—H), 1843, 1721 (νC═O), 1185 (νC—O) cm⁻¹.

FIFTEENTH EXAMPLE

[0141] The present inventors further synthesized another derivative ofnorbornene expressed as follows.

[0142] The derivative of norbornene was expressed by the general formula(4)

[0143] where R¹, R⁴, R⁵ and R⁶ were hydrogen atoms, R² and R³ weremethyl groups, R⁷ and R⁸ were propylene groups, i.e., [—(CH₂)₃—] bondedto each other for forming a ring and n was 1.

[0144] The derivative of norbornene was synthesized as similar to thatof the fourteenth example except that the present inventors usedacrylate of the second example instead of the acrylate of the thirdexample.

SIXTEENTH EXAMPLE

[0145] The present inventors synthesized polymer in norbornene series.The polymer contained a structural unit expressed by the general formula(4′) at 50 mole % and another structural unit expressed by the generalformula (4′a) at 50 mole %. The structural units were expressed by thefollowing structural formulae.

[0146] The first structural unit was expressed by the general formula(4′) where R¹, R², R³, R⁴, R⁵ and R⁶ were hydrogen atoms, R⁷ and R⁸ werepropylene groups, i.e., [—(CH₂)₃—] bonded to each other for forming aring and n was 1. On the other hand, the second structural unit wasexpressed by the general formula (4′a) where R¹³ was hydrogen atom andR¹⁴ was t-butoxycarbonyl group.

[0147] The derivative of norbornene was synthesized as follows. 0.131gram of di-μ-chlorobis [(η-allyl) palladium (II)] and 0.244 gram ofhexafluorosilver antimonate were dissolved in 22 milliliters ofchlorobenzene, and were agitated at room temperature. After 20 minutes,the reactant mixture was filtrated, and the filtrate was added tomixture containing 11.44 grams of the derivative of norbornene of thefourteenth example, 7.03 grams of 5-norbornene-2-carboxylic acid t-butylester, 0.1 milliliter of water and 85 milliliters of chlorobenzene. Thesolution was agitated for 20 hours at room temperature, and, thereafter,was added to 600 milliliters of methanol. Resin was precipitated, andwas filtrated. The resin was dissolved in 75 milliliters ofchlorobenzene, and 15 milliliters of methanol and 1.6 grams of sodiumborohydride were added thereto. Agitation was continued for 3 hours atroom temperature, and the solution was left as it was for 24 hours atroom temperature. Pd (0) particles were precipitated. The particles werefiltrated, and the filtrate was poured in 500 milliliters of methanolResin was precipitated, and was filtrated. Then, 8.86 grams of theobjective resin was obtained. The yield was 48%. The weight averagemolecular weight Mw was 13000, and the degree of dispersion Mw/Mn was2.36.

SEVENTEENTH EXAMPLE

[0148] The present inventors synthesized polymer in norbornene serieswhich contained a structural unit expressed by the general formula (4′)at 25 mole %, another structural unit expressed by the general formula(4′b) at 25 mole % and yet another structural unit expressed by thegeneral formula (4′c) at 50 mole %. The structural units were expressedas follows.

[0149] The first structural unit was expressed by the general formula(4′) where R¹, R², R³, R⁴, R⁵ and R⁶ were hydrogen atoms, R⁷ and R⁸ werepropylene groups, i.e., [—(CH₂)₃—] bonded to each other for forming aring and n was 1. On the other hand, the second structural unit wasexpressed by the general formula (4′b) where R¹⁵ was hydrogen atom andR¹⁶ was t-butoxycarbonyl group.

[0150] The polymer was synthesized as follows. 2 grams of the derivativeof norbornene of the fourteenth example, 1.646 grams of3-tetracyclododecene-8-carboxylic acid t-butyl ester and 1.24 grams ofmaleic anhidride were dissolved in 10 milliliters of tetrahydrofuran ina 100 ml flask with a reflux tube. 41.5 milligrams of AIBN was added tothe solution, and was agitated in argon atmosphere at 60 degrees to 65degrees in centigrade. After 20 hours, the resultant solution wascooled, and the reactant mixture was poured into 100 milliliters ofether. The precipitate was filtrated, and was refined through theprecipitation, again. Then, 1.5 grams of polymer was obtained. The yieldwas 31%.

[0151] The polymer was analyzed. The weight average molecular weight Mwwas determined to be 5700 through GPC analysis, and the degree ofdispersion Mw/Mn was 2.34.

[0152] Evaluations

[0153] The present inventors evaluated the polymer and chemicallyamplified resist as follows.

[0154] Resistance Against Etching

[0155] 2 grams of the polymer of the fourth example was dissolved in 10grams of propyleneglycolmonoethylether acetate, and the solution waspassed through a 0.2 micron Teflon filter. Subsequently, the filtratewas spun onto a 3-inch silicon wafer, and, thereafter, was baked on ahot plate at 90 degrees in centigrade for 60 seconds. A thin resistlayer of 0.7 micron thick was formed on the silicon wafer. The siliconwafer was put into a chamber of a reactive ion etching system, which wasmanufactured and sold by Nichiden-Anerba Corporation as DEM451. CF₄ gaswas supplied into the chamber, and dry etching was carried out on theconditions that the electric power was 100 watts, pressure was 5 Pa andgas flow was 30 sccm. After the dry etching, the resistance against thedry etching was evaluated on the basis of the etching speed.

[0156] The resistance against the dry etching was evaluated for thepolymer of the ninth example and the polymer of the sixteenth example assimilar to the polymer of the fourth example.

[0157] As comparative examples, novolak resist, poly (p-vinylphenol) andpoly (methylmethacrylate) were evaluated as similar to the fourth, ninthand sixteenth examples. The poly (p-vinylphenol) was used as the basicresin for KrF resist. The novolak resist and the poly (p-vinylphenol)were sold in the market The poly (methylmethacrylate) did not have anybridged cyclic hydrocarbon group in the molecular structure. The valuesof the etching speed were normalized with respect to that of the novolakresist as shown in the following table. Etching Speed Polymer (RelativeRatio) Example 4 1.2 Example 9 1.15 Example 16 1.15 Poly(methylmethacrylate) 1.9 Poly (p-vinylphenol) 1.2 Novolak Resist (PFI-15A) 1

[0158] The etching on the polymers according to the present inventionwas slower than that on the poly (p-vinylphenol). Thus, the polymersaccording to the present invention exhibited large resistance againstthe dry etching.

[0159] Transparency

[0160] 1.8 grams of the polymer of the fourth example was dissolved in10 grams of propyleneglycolmonoethylether acetate, and the solution wasfiltrated through a 0.2 micron Teflon filter. Subsequently, the filtratewas spun onto a 3-inch quartz plate, and, thereafter, was baked on a hotplate at 90 degrees in centigrade for 60 seconds. A thin resist layer of0.4 micron thick was formed on the quartz plate. Using anultra-violet/visual range spectrophotometer, the present inventorsmeasured the transmittance to 193.4 nm wavelength ray, which was thecentral wavelength of ArF excimer laser light.

[0161] The transparency was also evaluated for the polymer in theacrylic series, i.e., the ninth example and the polymer in thenorbornene series, i.e., the sixteenth example as similar to the polymerof the fourth example.

[0162] The transmittance of the fourth example was 83%/0.4 micron, thetransmittance of the ninth example was 81%/0.4 micron, and thetransmittance of the sixteenth example was 73%/0.4 micron. The presentinventors concluded that the polymers according to the present inventionexhibited transparency large enough to use it as a single layer resist.

[0163] Pattern Forming Property

[0164] The present inventors produced solution containing

[0165] (1) 2 grams of polymer in acrylic series obtained as the fourthexample,

[0166] (2) 0.04 gram of triphenylsulfonium nonaflate serving asphoto-acid generator, and

[0167] (3) 11.5 grams of propyleneglycolmonoethylether acetate.

[0168] The present inventors filtrated the solution with a 0.2 micronTeflon filter, and produced a chemically amplified resist.

[0169] An 8-inch silicon wafer was coated with 0.1 micron organicanti-reflection layer, which was manufactured by Brewer Corporation asDUV-30J, and the chemically amplified resist was spun thereonto. Thechemically amplified resist was baked on a hot plate at 110 degrees incentigrade for one minute. Then, the anti-reflection layer was overlaidby a chemically amplified resist layer of 0.4 micron thick.

[0170] The silicon wafer coated with the chemically amplified resistlayer was put into an ArF reduction projection aligner, which wasmanufactured by Nikon Corporation. The numerical aperture was 0.6.. Thechemically amplified resist layer was exposed to ArF excimer laser lightso as to form a latent image therein.

[0171] After the exposure to the light, the silicon wafer was baked onthe hot plate at 130 degrees in centigrade for 60 seconds, and,thereafter, was dipped in 2.38% water solution of (CH₃)₄ NOH (TMAH) for60 seconds. The latent image was developed. After the development, thechemically amplified resist layer was rinsed in pure water for 60seconds, and a positive resist pattern was formed on the silicon wafer.

[0172] The present inventors similarly produced another sort ofchemically amplified resist on the basis of the polymer in acrylicseries produced as the ninth example and yet another sort of chemicallyamplified resist one the basis of the polymer in norbornene seriesproduced as the sixteenth example. Using these sorts of chemicallyamplified resist, the positive pattern was transferred to the chemicallyamplified resist layers as similar to the above.

[0173] The present inventors evaluated those sorts of chemicallyamplified resist from the viewpoints of sensitivity and resolution. Theevaluation was summarized in the following table. Chemically AmplifiedResist Resolution Sensitivity Containing (μmL/S) (mJ/cm²) Fourth example0.14 20.4 Ninth example 0.13 15.6 Sixteenth example 0.15 22.0

[0174] Thus, the present inventors concluded that the chemicallyamplified resist according to the present invention exhibited goodpattern forming property.

[0175] Adhesion to Substrates

[0176] The present inventors spread the chemically amplified resistaccording to the present invention on substrates, and observed theboundary between the chemically amplified resist layers and thesubstrates through a scanning electron microscopy. The chemicallyamplified resist layers were strongly adhered to the substrates, and didnot peel off. Thus, the present inventors concluded that the chemicallyamplified resist had good adhesion to substrates.

[0177] The present inventors evaluated other sorts of chemicallyamplified resist produced on the basis of other polymers in similarmanners to those described hereinbefore. The results were summarized asfollows.

[0178] The present inventors confirmed that chemically amplified resistproduced on the basis of the polymer in acrylic series, i.e., each ofthe fifth to eighth and tenth to thirteenth examples exhibited largeresistance against etching, high transparency, high sensitivity, goodresolution and good adhesion to substrates.

[0179] The present inventors further confirmed that chemically amplifiedresist produced on the basis of the polymer in norbornene series, i.e.,the seventeenth example exhibited large resistance against etching, hightransparency, high sensitivity, good resolution and good adhesion tosubstrates. The present inventors further synthesized a derivative of(meth)acrylate expressed by the general formula (3) where n is zero. Aderivative of 3-oxo-4-oxabicyclo [3.2.1] octane reacted withtriphenylmethyllithium and, thereafter, with 1,2-dibromoethane to2-bromo compound. The 2-bromo compound reacted with (meth)acrylic acidin the presence of basic catalyst. Then, the present inventors obtained(meth)acrylate expressed by the general formula (3) where n is zero. Thederivative of (meth)acrylate reacted with cyclopentadiene. Then, aderivative of norbornene at n=zero was obtained. The monomers, i.e., thederivative of (meth)acrylate and the derivative of norbornene were vinylpolymerized to obtain polymer. Chemically amplified resist was producedon the basis of the polymer, and the present inventors evaluated thechemically amplified resist. The present inventors confirmed that thechemically amplified resist exhibited large resistance against etching,high transparency, high sensitivity, good resolution and good adhesionto substrates.

[0180] As will be appreciated from the foregoing description, thepolymer and chemically amplified resist according to the presentinvention have the bridged alicylic δ lactone structure so that thelarge resistance against dry etching, high transparency, good resolutionand good adhesion to substrates are achieved. Using the chemicallyamplified resist, the manufacturer can transfer fine patterns to siliconwafers in the fabrication process of ultra large scale integration inthe next generation.

[0181] Although particular embodiments of the present invention havebeen shown and described, it will be apparent to those skilled in theart that various changes and modifications may be made without departingfrom the spirit and scope of the present invention.

What is claimed is:
 1. Monomer for a chemically amplified photoresistcomprising vinyl monomer having 3-oxo-4-oxabicyclo [3.2.1] octane-2-ylgroup expressed by general formula (1)

where each of L¹, L², L³, L⁴ L⁵ and L⁶ is selected from the groupconsisting of hydrogen atom and alkyl groups having the carbon numberfrom 1 to
 8. 2. The monomer as set forth in claim 1, in which one ofsaid hydrogen atom and said alkyl groups at L⁵ and one of said hydrogenatom and said alkyl groups at said L⁶ are replaced with alkylene groupshaving the carbon number from 1 to 10 and bonded to each other forforming a ring.
 3. The monomer as set forth in claim 1, in which saidvinyl monomer has a structure selected from the group consisting ofethylene, derivatives of ethylene, vinyl chloride, derivatives of vinylchloride, styrene, derivatives of styrene, acrylonitrile, derivatives ofacrylonitrile, (meth)acrylate, derivatives of (meth)acrylate, norbornenecarboxylic acid ester and derivatives of norbornene carboxylic acidester.
 4. The monomer as set forth in claim 3, in which said derivativesof (meth)acrylate have a bridged alicylic δ lactone structure expressedby general formula (3)

where R¹ is selected from the group consisting of hydrogen atom andmethyl group, each of R² and R³ is selected from the group consisting ofhydrogen atom and alkyl groups having the carbon numbers from 1 to 4,each of R⁴, R⁵ and R⁶ is selected from the group consisting of hydrogenatom and methyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groupshaving the carbon number from 1 to 10 and bonded to each other forforming a ring and n is zero or
 1. 5. The monomer as set forth in claim3, in which said derivatives of norbornene carboxylic acid ester have abridged alicylic δ lactone structure expressed by general formula (4)

where R¹ is selected from the group consisting of hydrogen atom andmethyl group, each of R² and R³ is selected from the group consisting ofhydrogen atom and alkyl groups having the carbon number from 1 to 4,each of R⁴, R⁵ and R⁶ is selected from the group consisting of hydrogenatom and methyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groupshaving the carbon number from 1 to 10 and bonded to each other forforming a ring and n is zero or
 1. 6. Monomer for a chemically amplifiedphotoresist comprising vinyl monomer having a bridged alicylic δ lactonestructure expressed by general formula (2)

where each of R² and R³ is selected from the group consisting ofhydrogen and alkyl groups having the carbon number from 1 to 4, each ofR⁴, R⁵ and R⁶ is selected from the group consisting of hydrogen atom andmethyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groups eachhaving the carbon number from 1 to 10 and bonded for forming a ring andn is zero or
 1. 7. The monomer as set forth in claim 6, in which saidvinyl monomer has a structure selected from the group consisting ofethylene, derivatives of ethylene, vinyl chloride, derivatives of vinylchloride, styrene, derivatives of styrene, acrylonitrile, derivatives ofacrylonitrile, (meth)acrylate, derivatives of (meth)acrylate, norbornenecarboxylic acid ester and derivatives of norbornene carboxylic acidester.
 8. The monomer as set forth in claim 7, in which said derivativesof (meth)acrylate have a bridged alicylic δ lactone structure expressedby general formula (3)

where R¹ is selected from the group consisting of hydrogen atom andmethyl group, each of R² and R³ is selected from the group consisting ofhydrogen atom and alkyl groups having the carbon numbers from 1 to 4,each of R⁴, R⁵ and R⁶ is selected from the group consisting of hydrogenatom and methyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groupshaving the carbon number from 1 to 10 and bonded to each other forforming a ring and n is zero or
 1. 9. The monomer as set forth in claim7, in which said derivatives of norbornene carboxylic acid ester have abridged alicylic δ lactone structure expressed by general formula (4)

where R¹ is selected from the group consisting of hydrogen atom andmethyl group, each of R² and R³ is selected from the group consisting ofhydrogen atom and alkyl groups having the carbon number from 1 to 4,each of R⁴, R⁵ and R⁶ is selected from the group consisting of hydrogenatom and methyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groupshaving the carbon number from 1 to 10 and bonded to each other forforming a ring and n is zero or
 1. 10. Polymer used for a chemicallyamplified photoresist comprising vinyl polymer having 3-oxo-4-oxabicyclo[3.2.1] octane-2-yl group expressed by general formula (1)

where each of L¹, L², L³, L⁴, L⁵ and L⁶ is selected from the groupconsisting of hydrogen atom and alkyl groups having the carbon numberfrom 1 to
 8. 11. The polymer as set forth in claim 10, in which one ofsaid hydrogen atom and said alkyl groups at L⁵ and one of said hydrogenatom and said alkyl groups at said L⁶ are replaced with alkylene groupshaving the carbon number from 1 to 10 and bonded to each other forforming a ring.
 12. The polymer as set forth in claim 10, in which saidvinyl polymer comprises at least one structural unit polymerized withvinyl monomer selected from the group consisting of ethylene,derivatives of ethylene, vinyl chloride, derivatives of vinyl chloride,styrene, derivatives of styrene, acrylonitrile, derivatives ofacrylonitrile, (meth)acrylate, derivatives of (meth)acrylate, norbornenecarboxylic acid ester and derivatives of norbornene carboxylic acidester.
 13. The polymer as set forth in claim 12, in which the vinylpolymers in acrylic series have a bridged alicylic δ lactone structureexpressed by general formula (3′)

where R¹ is selected from the group consisting of hydrogen atom andmethyl group, each of R² and R³ is selected from the group consisting ofhydrogen atom and alkyl groups having the carbon numbers from 1 to 4,each of R⁴, R⁵ and R⁶ is selected from the group consisting of hydrogenatom and methyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groupshaving the carbon number from 1 to 10 and bonded to each other forforming a ring and n is zero or
 1. 14. The polymer as set forth in claim12, in which the vinyl polymers in norbornene series have a bridgedalicylic δ lactone structure expressed by general formula (4′)

where R¹ is selected from the group consisting of hydrogen atom andmethyl group, each of R² and R³ is selected from the group consisting ofhydrogen atom and alkyl groups having the carbon number from 1 to 4,each of R⁴, R⁵ and R⁶ is selected from the group consisting of hydrogenatom and methyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groupshaving the carbon number from 1 to 10 and bonded to each other forforming a ring and n is zero or
 1. 15. The polymer as set forth in claim13, said vinyl polymer further comprises at least one structural unit isexpressed by one of the general formulae (3′a), (3′b) and (3′c)

where R⁹ is selected from the group consisting of hydrogen atom andmethyl group, R¹⁰ is selected from the group consisting of groups to bedecomposed by acid and bridged cyclic hydrocarbon groups having thecarbon number from 7 to 13 and having groups to be decomposed by acid,R¹¹ is selected from the group consisting of hydrogen atom and methylgroup, R¹² is selected from the group consisting of hydrogen atom,hydrocarbon groups having the carbon number from 1 to 12, bridged cyclichydrocarbon groups having the carbon number from 7 to 13 and eitherhydroxy or carboxy group and 2,6-norbornanecarbolactone-5-yl group and Mis selected from the group consisting of hydrogen atom, hydroxy group,hydroxyalkyl groups and acid dissociated organic groups having thecarbon number equal to or less than 20 and to be decomposed by acid forproducing carboxyl group.
 16. The polymer as set forth in claim 14, inwhich said vinyl polymer further comprises another structural unitexpressed by one of the general formulae (4′a), (4′b) and (4′c)

where R¹³ is selected from the group consisting of hydrogen atom andmethyl group, R¹⁴ is selected from the group consisting of hydroxygroup, hydroxyalkyl group and acid dissociated organic groups having thecarbon number equal to or less than 20 and to be decomposed by acid forproducing carboxy group, R¹⁵ is selected from the group consisting ofhydrogen atom and methyl group and R¹⁶ is selected from the groupconsisting of hydroxy group, hydroxyalkyl group and acid dissociatedorganic groups having the carbon number equal to or less than 20 and tobe decomposed by acid for producing carboxy group.
 17. The polymer asset forth in claim 13, in which the ratio of vinyl monomers with saidbridged alicylic δ lactone structure expressed by general formula (3′)to said vinyl polymer is fallen within the range between 5 mole % and 90mole %.
 18. The polymer as set forth in claim 14, in which the ratio ofsaid vinyl monomers with said bridged alicylic δ lactone structureexpressed by general formula (4′) to said vinyl polymer is fallen withinthe range between 5 mole % and 90 mole %.
 19. The polymer as set forthin claim 10, in which said vinyl polymer has the weight averagemolecular weight ranging from 2,000 to 200,000.
 20. Polymer used for achemically amplified photoresist comprising vinyl polymer having abridged alicylic δ lactone structure expressed by general formula (2)

where each of R² and R³ is selected from the group consisting ofhydrogen and alkyl groups having the carbon number from 1 to 4, each ofR⁴, R⁵ and R⁶ is selected from the group consisting of hydrogen atom andmethyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groups eachhaving the carbon number from 1 to 10 and bonded for forming a ring andn is zero or
 1. 21. The polymer as set forth in claim 20, in which saidvinyl polymer comprises at least one structural unit polymerized withvinyl monomer selected from the group consisting of ethylene,derivatives of ethylene, vinyl chloride, derivatives of vinyl chloride,styrene, derivatives of styrene, acrylonitrile, derivatives of acrylonitrile, (meth)acrylate, derivatives of (meth)acryl ate, norbornenecarboxylic acid ester and derivatives of norbornene carboxylic acidester.
 22. The polymer as set forth in claim 21, in which the vinylpolymers in acrylic series have a bridged alicylic δ lactone structureexpressed by general formula (3′)

where R¹ is selected from the group consisting of hydrogen atom andmethyl group, each of R² and R³ is selected from the group consisting ofhydrogen atom and alkyl groups having the carbon numbers from 1 to 4,each of R⁴, R⁵ and R⁶ is selected from the group consisting of hydrogenatom and methyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groupshaving the carbon number from 1 to 10 and bonded to each other forforming a ring and n is zero or
 1. 23. The polymer as set forth in claim21, in which the vinyl polymers in norbornene series have a bridgedalicylic δ lactone structure expressed by general formula (4′)

where R¹ is selected from the group consisting of hydrogen atom andmethyl group, each of R² and R³ is selected from the group consisting ofhydrogen atom and alkyl groups having the carbon number from 1 to 4,each of R⁴, R⁵ and R⁶ is selected from the group consisting of hydrogenatom and methyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groupshaving the carbon number from 1 to 10 and bonded to each other forforming a ring and n is zero or
 1. 24. The polymer as set forth in claim22, in which said vinyl polymer further comprises at least onestructural unit is expressed by one of the general formulae (3′a), (3′b)and (3′c)

where R⁹ is selected from the group consisting of hydrogen atom andmethyl group, R¹⁰ is selected from the group consisting of groups to bedecomposed by acid and bridged cyclic hydrocarbon groups having thecarbon number from 7 to 13 and having groups to be decomposed by acid,R¹¹ is selected from the group consisting of hydrogen atom and methylgroup, R¹² is selected from the group consisting of hydrogen atom,hydrocarbon groups having the carbon number from 1 to 12, bridged cyclichydrocarbon groups having the carbon number from 7 to 13 and eitherhydroxy or carboxy group and 2,6-norbornanecarbolactone-5-yl group and Mis selected from the group consisting of hydrogen atom, hydroxy group,hydroxyalkyl groups and acid dissociated organic groups having thecarbon number equal to or less than 20 and to be decomposed by acid forproducing carboxy group.
 25. The polymer as set forth in claim 23, inwhich said vinyl polymer further comprises another structural unitexpressed by one of the general formulae (4′a), (4′b) and (4′c)

where R¹³ is selected from the group consisting of hydrogen atom andmethyl group, R¹⁴ is selected from the group consisting of hydroxygroup, hydroxyalkyl group and acid dissociated organic groups having thecarbon number equal to or less than 20 and to be decomposed by acid forproducing carboxy group, R¹⁵ is selected from the group consisting ofhydrogen atom and methyl group and R¹⁶ is selected from the groupconsisting of hydroxy group, hydroxyalkyl group and acid dissociatedorganic groups having the carbon number equal to or less than 20 and tobe decomposed by acid for producing carboxy group.
 26. The polymer asset forth in claim 22, in which the ratio of structural unit with saidbridged alicylic δ lactone structure expressed by general formula (3′)to said vinyl polymer is fallen within the range between 5 mole % and 90mole %.
 27. The polymer as set forth in claim 23, in which the ratio ofsaid structural unit with said bridged alicylic δ lactone structureexpressed by general formula (4′) to said vinyl polymer is fallen withinthe range between 5 mole % and 90 mole %.
 28. The polymer as set forthin claim 20, in which said vinyl polymer has the weight averagemolecular weight ranging from 2,000 to 200,000.
 29. Photoresistcomprising polymer including vinyl polymer having o-oxo-4-oxabicyclo[3.2.1] octane-2-yl group expressed by general formula (1)

where each of L¹, L², L³, L⁴, L⁵ and L⁶ is selected from the groupconsisting of hydrogen atom and alkyl groups having the carbon numberfrom 1 to 8, and photo-acid generator generating acid in the presence oflight equal in wavelength to or less than 220 nanometers, the ratio ofsaid photo-acid generator to said photoresist being fallen within therange from 0.2% by mass to 30% by mass.
 30. The photoresist as set forthin claim 29, in which one of said hydrogen atom and said alkyl groups atL⁵ and one of said hydrogen atom and said alkyl groups at said L⁶ arereplaced with alkylene groups having the carbon number from 1 to 10 andbonded to each other for forming a ring.
 31. The photoresist as setforth in claim 29, in which said vinyl polymer comprises at least onestructural unit polymerized with vinyl monomer selected from the groupconsisting of ethylene, derivatives of ethylene, vinyl chloride,derivatives of vinyl chloride, styrene, derivatives of styrene,acrylonitrile, derivatives of acrylonitrile, (meth)acrylate, derivativesof (meth)acrylate, norbornene carboxylic acid ester and derivatives ofnorbornene carboxylic acid ester.
 32. The polymer as set forth in claim31, in which the vinyl monomers in acrylic series have a bridgedalicylic δ lactone structure expressed by general formula (3′)

where R¹ is selected from the group consisting of hydrogen atom andmethyl group, each of R² and R³ is selected from the group consisting ofhydrogen atom and alkyl groups having the carbon numbers from 1 to 4,each of R⁴, R⁵ and R⁶ is selected from the group consisting of hydrogenatom and methyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groupshaving the carbon number from 1 to 10 and bonded to each other forforming a ring and n is zero or
 1. 33. The polymer as set forth in claim31, in which the vinyl polymers in norbornene series have a bridgedalicylic δ lactone structure expressed by general formula (4′)

where R¹ is selected from the group consisting of hydrogen atom andmethyl group, each of R² and R³ is selected from the group consisting ofhydrogen atom and alkyl groups having the carbon number from 1 to 4,each of R⁴, R⁵ and R⁶ is selected from the group consisting of hydrogenatom and methyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groupshaving the carbon number from 1 to 10 and bonded to each other forforming a ring and n is zero or
 1. 34. Photoresist comprising polymerincluding vinyl polymer having a bridged alicylic δ lactone structureexpressed by general formula (2)

where each of R² and R³ is selected from the group consisting ofhydrogen and alkyl groups having the carbon number from 1 to 4, each ofR⁴, R⁵ and R⁶ is selected from the group consisting of hydrogen atom andmethyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groups eachhaving the carbon number from 1 to 10 and bonded for forming a ring andn is zero or 1, and photo-acid generator generating acid in the presenceof light equal in wavelength to or less than 220 nanometers, the ratioof said photo-acid generator to said photoresist being fallen within therange from 0.2% by mass to 30% by mass.
 35. The photoresist as set forthin claim 34, in which said vinyl polymer comprises at least onestructural unit polymerized with vinyl monomer selected from the groupconsisting of ethylene, derivatives of ethylene, vinyl chloride,derivatives of vinyl chloride, styrene, derivatives of styrene,acrylonitrile, derivatives of acrylonitrile, (meth)acrylate, derivativesof (meth)acrylate, norbornene carboxylic acid ester and derivatives ofnorbornene carboxylic acid ester.
 36. The photoresist as set forth inclaim 35, in which the vinyl polymers in acrylic series have a bridgedalicylic δ lactone structure expressed by general formula (3′)

where R¹ is selected from the group consisting of hydrogen atom andmethyl group, each of R² and R³ is selected from the group consisting ofhydrogen atom and alkyl groups having the carbon numbers from 1 to 4,each of R⁴, R⁵ and R⁶ is selected from the group consisting of hydrogenatom and methyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groupshaving the carbon number from 1 to 10 and bonded to each other forforming a ring and n is zero or
 1. 37. The polymer as set forth in claim35, in which the vinyl polymers in norbornene series have a bridgedalicylic δ lactone structure expressed by general formula (4′)

where R¹ is selected from the group consisting of hydrogen atom andmethyl group, each of R² and R³ is selected from the group consisting ofhydrogen atom and alkyl groups having the carbon number from 1 to 4,each of R⁴, R⁵ and R⁶ is selected from the group consisting of hydrogenatom and methyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groupshaving the carbon number from 1 to 10 and bonded to each other forforming a ring and n is zero or
 1. 38. The polymer as set forth in claim15, in which said at least one structural units expressed by saidgeneral formulae (3′a) to (3¹c) is copolymerized with one of thestructural units expressed by said general formula (3′) and the generalformula (4′)


39. The polymer as set forth in claim 24, in which said at least onestructural units expressed by said general formulae (3′a) to (3′c) iscopolymerized with one of the structural units expressed by said generalformula (3′) and the general formula (4′)


40. The polymer as set forth in claim 16, in which said anotherstructural unit expressed by one of the general formulae (4′a), (4′b)and (4′c) is copolymerized with one of the structural units expressed bysaid general formula (4′) and the general formula (3′)


41. The polymer as set forth in claim 25, in which said anotherstructural unit expressed by one of the general formulae (4′a), (4′b)and (4′c) is copolymerized with one of the structural units expressed bysaid general formula (4′) and the general formula (3′)


42. The polymer as set forth in claim 16, in which said anotherstructural unit expressed by one of the general formulae (4′a), (4′b)and (4′c) is copolymerized with at least one of the structural unitsexpressed by said general formula (3′a), (3′b) and (3′c)


43. The polymer as set forth in claim 25, in which said anotherstructural unit expressed by one of the general formulae (4′a), (4′b)and (4′c) is copolymerized with at least one of the structural unitsexpressed by said general formula (3′a), (3b) and (3′c)


44. A method for transferring a pattern to a photoresist layer,comprising the steps of: a) preparing a substrate having at least onelayer and photoresist comprising polymer including vinyl polymer having3-oxo-4-oxabicyclo [3.2.1] octane-2-yl group expressed by generalformula (1)

where each of L¹, L², L³, L⁴, L⁵ and L⁶ is selected from the groupconsisting of hydrogen atom and alkyl groups having the carbon numberfrom 1 to 8 and photo-acid generator generating acid in the presence oflight equal in wave-length to or less than 220 nanometers, the ratio ofsaid photo-acid generator to said photoresist being fallen within therange from 0.2% by mass to 30% by mass; b) spreading said photoresist onsaid layer for forming a photoresist layer; c) exposing said photoresistlayer to image-carrying light having a wave-length between 180nanometers and 220 nanometers for forming a latent image in saidphotoresist layer; and d) developing said latent image so as to patternsaid photoresist layer into a photoresist patterned layer.
 45. Themethod as set forth in claim 44, in which said light is ArF excimerlaser light.
 46. The method as set forth in claim 44, in which one ofsaid hydrogen atom and said alkyl groups at L⁵ and one of said hydrogenatom and said alkyl groups at said L⁶ are replaced with alkylene groupshaving the carbon number from 1 to 10 and bonded to each other forforming a ring.
 47. The method as set forth in claim 44, in which saidvinyl polymer comprises at least one structural unit polymerized withvinyl monomer selected from the group consisting of ethylene,derivatives of ethylene, vinyl chloride, derivatives of vinyl chloride,styrene, derivatives of styrene, acrylonitrile, derivatives ofacrylonitrile, (meth)acrylate, derivatives of (meth)acrylate, norbornenecarboxylic acid ester and derivatives of norbornene carboxylic acidester.
 48. A method for transferring a pattern to a photoresist layer,comprising the steps of: a) preparing a substrate having at least onelayer and photoresist comprising polymer including vinyl polymer havinga bridged alicylic δ lactone structure expressed by general formula (2)

where each of R² and R³ is selected from the group consisting ofhydrogen and alkyl groups having the carbon number from 1 to 4, each ofR⁴, R⁵ and R⁶ is selected from the group consisting of hydrogen atom andmethyl group, R⁷ and R⁸ are hydrogen atoms or alkylene groups eachhaving the carbon number from 1 to 10 and bonded for forming a ring andn is zero or 1 and photo-acid generator generating acid in the presenceof light equal in wavelength to or less than 220 nanometers, the ratioof said photo-acid generator to said photo-resist being fallen withinthe range from 0.2% by mass to 30% by mass, b) spreading saidphotoresist on said layer for forming a photoresist layer; c) exposingsaid photoresist layer to image-carrying light having a wave-lengthbetween 180 nanometers and 220 nanometers for forming a latent image insaid photoresist layer; and d) developing said latent image so as topattern said photoresist layer into a photoresist patterned layer. 49.The method as set forth in claim 48, in which said light is ArF excimerlaser light.
 50. The method as set forth in claim 48, in which saidvinyl polymer comprises at least one structural unit polymerized withvinyl monomer selected from the group consisting of ethylene,derivatives of ethylene, vinyl chloride, derivatives of vinyl chloride,styrene, derivatives of styrene, acrylonitrile, derivatives ofacrylonitrile, (meth)acrylate, derivatives of (meth)acrylate, norbornenecarboxylic acid ester and derivatives of norbornene carboxylic acidester.